There are more than 2,200 species of fleas recognized worldwide. In North America, only a few species commonly infest dogs and cats: Ctenocephalides felis (the cat flea), C. canis (the dog flea), Pulex simulans (a flea of small mammals), and Echidnophaga gallinacea (the poultry sticktight flea). The most prevalent flea infesting dogs and cats is the cat flea (Ctenocephalides felis). Cat fleas are responsible for flea allergy dermatitis.
Flea allergy dermatitis (FAD), or flea bite hypersensitivity, is an immunologic disorder and the most common dermatological disease in domestic animals, specifically dogs and cats. FAD exhibits as a very itchy skin reaction or allergy and predisposes to the development of secondary skin infections and diseases. For instance, FAD is one of the major causes of feline miliary dermatitis in cats (also known as miliary eczema, papulocrusting dermatitis or scabby cat disease). FAD is caused by flea bites, specifically the saliva of the flea, which contains many antigenic materials such as amino acids, aromatic compounds, polypeptides, and phosphorous. Dogs and cats can develop flea saliva allergies at any point in their life, and once they have it, it is seldom rectified.
Adult cat fleas begin feeding almost immediately once they find a host, with many fleas feeding within minutes. Feeding is so rapid that partially digested blood can be defecated in as little as just a few minutes after fleas acquire a host. While initiation of feeding is rapid, daily blood consumption is voracious. Female cat fleas can consume up to 10 times their body weight in blood on the very first day they are on the host and peak consumption occurs within a few days at 15 times their body weight daily (13.6 μL of blood per day). After rapid transit through the flea, the excreted blood dries within minutes into reddish black fecal pellets or long tubular coils (“flea dirt”). Fleas mate after feeding and egg production begins within 24-48 hours of females taking their first blood meal. Female cat fleas can produce up to 40-50 eggs/day during peak egg production, averaging 27 eggs/day through 50 days, and may continue to produce eggs for more than 100 days. See “Fleas and Flea Allergy Dermatitis: Introduction”, The Merck Veterinary Manual, 9th Edition, 2005; Dryden, “Flea and tick control in the 21st century: challenges and opportunities”, Veterinary Dermatology, DOI: 10.1111/j.1365-3164.2009.00838.x.
An indirect indicator of an insecticide's ability to reduce blood consumption by fleas is the ability of the compound to kill fleas before they are able to lay eggs, thereby reducing egg production. Not only is reduction in egg production an indicator of reduced blood consumption, it is also important for modern day flea control. Several adulticides, such as fipronil, imidacloprid, metaflumizone, mitenpyram, selamectin, and spinosad have had a major impact on reducing the occurrence of FAD in dogs and cats. However, these compounds neither sufficiently stop flea bites nor sufficiently stop flea feeding. Therefore, it is assumed that the role of these compounds in managing FAD is more related to a decrease in flea feeding over a prolonged period of time rather that eliminating flea biting from occurring at all.
Accordingly, it would be desirable to provide methods for preventing fleas from taking a blood meal on the host animal thereby reducing the incidence of or preventing flea allergy dermatitis from occurring in the host animal. In particular, a need exists for prophylaxis of flea allergy dermatitis.